Control system for air compressors



M y 1933a A. c. STALEY 2,115,888

CdNTROL SYSTEM FOR AIR QOMPRESSORS Filed Oct. 2; 1935 5 Sheets-Sheet 1 INVENTOR. fi l r? 6'. 'SZaZe y.

May'3,' 1938. A. c. ST'ALEY I v CONTROL SYSTEM FOR AIR COMPRESSORS Filed oct, 2, 195's *5 Sheets-Sheet 2 filler C 52416} TTQRNEY y 1933 A. c. STALEYI 2,115,888

CONTROL SYSTEM FOR AIR COMPRE'SSORS 4 Filed 001;. 2, 1933 5 Sheets-Sheet 3 IIIIIIIIIIII INVENTOR. fiZZc??? C SJaZe y,

' ATTORNEY.

. May 3, 1938.

A. c. STALEY 2,115,888

CONTROL SYSTEM FOR AIR COMPRESSORS Filed Oct; 2, 1933 5 Sheets-Sheet 4 INVENTOR. File) 6'. Sialqy.

ATTORNEY.

1933- A. c. STALEY 2,115,888

.CONTROL SYSTEM FOR AIR COMPRESSORS Filed Oct. 2, 193a, 5 Sheets- Sheet 5 Carl ureforr Compress o r.

INVENTOR. v filler; C. 524% VATTORNEY.

Patented May 3, 1938 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOR AIR CiOmRESSORS Allen 0. Staley, Birmingham, Mich assignorto. Chrysler Corporation, Detroit, Mich a corporation-or Delaware Application October 2,

' 6 Claims.

This invention relates to power driven air 'compressors and more especially to control mechanism for regulating the operation of the same.

The main object of the invention is to improve the operation of a power driven air compressor.

A further object is to increase the eiiiciency of an air compressor.

Another object is to so control an air-compressor that it will operate at speeds in proportion to the demand for air.

Another. object is to reduce the operating cost' of an air compressor per cubic foot of air de livered.

Another object is to provide for a high volumetric eiliciency at normal operating speeds of an air compressor.

Another object is to reduce the temperature of the air delivered by an air compressor.

Another object is to avoid throttling of airrsupplied to an air compressor.

A still further object is to avoid hunting or fluttering in the control oi. the operation of an air compressor.

Other objects and advantages will become apparent from the following description and appended claims According to one aspect, this invention involves the control of a multicylinder air compressor operable by a multicyiinder internal combustion engine at speeds covering a wider rangethan customarily employed and at considerably higher speeds than usual when operating at or near full capacity. The compressor is loaded or unloaded by a had control valve placed inthe intake thereof and operable to fully open position and to fully closed positions. with the compressor loaded, the speed of the engine is controlled by a speed governing mechanism adapted to control the intake throttle valve of its carburetor and the speed governing mechanism is under the control of pressure responsive mecha-. nism operable in accordance with increasing or decreasing pressures above a predetermined point in an air tank; to which compressedair is supplied by the air compressor, to act on the speed gov erning' mechanism gradually to cut 'down or increase the speed of the engine. above a higher predetermined .point in the air tank causes means operable by the pressure responsive I means, at one limit of its operation, to act on valve operating-means and cause the load control valve in the intake of the compressor to assume its fully closed position to unload the compressor.

A drop in pressure in the air tank to a third predetermined value somewhat less than said second- 1933. Serial No. 691,813

named predetermined value causes pressure responsive means to'allow the valve-operating means to open theload control valve and load the compressor.

According to another aspect, the invention involves the control 01' an air compressor so that it is loaded from approximately one quarter to full capacity, givinglow speeds and low friction during part capacity operation and during almost wide open throttle operation of the engine by which the compressor is operated while at full capacity.

This effects a considerable economy of fuel and increased life of equipment as compared with compressors employing control systems of the type that vary the amount of idle operation so that a.

certain per cent of idling is always used up until iull capacity operation is reached. The present system causes idling only when the compressor is operating at a small fraction or full capacity and' results in a saving of up to fifty per cent in fuel consumption. a

For the purpose of illustrating .the genus of .the invention, a typical concrete embodiment is shown in the accompanying drawings in connection with a portable compressor unit.

In the drawings:

Figure 1 is a top plan, more or less diagram matic in form, and with parts broken away to show interior parts, 01 a portable compressor unit in the form of a trailer and embodying a control system'in accordance with the principles of this invention; 1-

Fig. 2 is a section taken on the line 2- -2 otFig.

'1, certain portions being shown in elevation;

Fig. 3 is a section taken on the lin'eI-S of Fig. 2, parts being broken away and shown in sections;

Fig. 4 isa section taken on the line 4-4' of 8. 3; a Y Fig. 5 is a section taken on the line H of Fig. 1; i I Fig. 6 is a section Fig. 5:

Fig. 7 is a graphical representation showing air taken 8.. the use 0-! oi by a wheel and axle assembly I I. Upon opposite sides of the frame III are supported an engine I2 and a compressor I3 connected by a suitable drive and speed reduction means'such as a pair of drums I4 and I5 and a plurality of v belts I5 extending therebetween, the pulley I4 being of a smaller diameter than the pulley I5 in the ratio of approximately 1 to 1.59 to reduce the operating speed of the compressor by approximately this ratio. The engine I2 and compressor I3 each includes the'same size cylinder block of a conventional fourcylinde'r industrial engine of the four cycle type with the cylinders, cast in block integral with the crank case so that the engine and compressor are of the same size and are made up largely of interchangeable parts to make servicing of these units a simple problem. Each of these units is provided. with an individual cooling systein including a radiator I1 and fan'IB. The

compressor is provided with an intake manifold adapted to draw in air through a conduit 2I in which is disposed a load control valve 22, shown more indetail in Figs. 5 and 6, and which will later be more fully described. The com pressor I3 delivers air through an. exhaust manifold 23 connected to the individual cylinders of the compressor and through a delivery conduit 24 communicating with an air tank 25-supported between converging portions of the side rails of frame III. The air tank 25 is provided with a plurality of delivery valves 26 for supplying air to air driven devices, such as for example, from one to four air drills or similar air driven tools. A conduit 21 communicates between the air tank 25 and a pressure responsive mechanism 30 adapted to cooperate with a speed control mech anism for the engine I2 or other motive means for driving thifi'iompressor I3. The pressure responsive device and the speed control means 3I are shown more in detail in Figs. 2 and 3. The pressure responsive device 30 also controls the operation of a switch 32 which in turn controls the operation of operating means for the valve 22 in the intake conduit 2I of the compressor.

Reference may now be had to Figs. 2, 3 and 4 which illustrate the construction and arrangement of the pressure responsive device, the speed control mechanism for controlling the operation of the motive means for the compressor, and the switch for controlling the operation of the intake valve for the compressor. The units 30, 3| and 32 are mounted on a plate 33 fixed to the block of engine I2. The unit 30 is in the-form of a cylinder in which is disposed-a movable piston on preferably a sylphon bellows 34 normally biased to the right hand end position as viewed in Fig. 2 by means of a spring 35. The conduit 21 communicating with the air tank 25 is connected to a cylinder head 36 for the casing of the pressure responsive device 30 so that the pressure within the tank .25 is impressed upon the head surface the pressure responsive device and pivoted to the plate member 33 by means of a pivot pin 43 supported in a bracket 44 fixed .to the plate 33.

The speed control mechanism 3| is in the form of a governor or other speed control device operable by the engine I2 or the compressor I3 and includes a control arm adapted-to rotate in a clockwise direction as viewed in Fig. 2 in redepressed position.

sponse to increasing speeds of the motive means I2. 'The speed control mechanism 3I, as illustrated, is operated by means of a gear 5| from the engine I2 and in response to higher speeds of the engine rotates the arm 50 in a clockwise direction against the tension of a governor spring 52 connecting an arm 53 of the control lever 54 to the lever 4 I. The outer end of the arm 50 may be connected by means of a link 54 to' the throttle duce the speed of the engine I2. The lever 4| is fixed against relative rotation to the pivot pin 43 and serves not only to rotate the control lever 50 in the event of high pressures within the tank 25 but also at certain predetermined pressures in tank 25 to actuate the switch 32. To this end an arm 55 is also fixed against relative rotation upon the pivot pin 43 and is provided with an adjustable screw 56 upon the free end of this lever arm eooperable with a contact arm 51 pivoted upon a switch bracket 59 by means of the pivot pin 58. The switch bracket 53 carries a terminal 60 for a circuit, (Fig. 8), to which the switch 32 is connected. The contact arm 51 carries a movable contact 6| cooperable with a contact 62 carried on a spring arm 63 mounted on a switch bracket 64 but insulated therefrom by insulation means 65. The spring arm 63 carries a flexible spring leaf 56 .cooperablewith a similar leaf 61 connected to one end of the winding of an electro-magnet 10 disposed beneath the spring arm 63 and positioned to actuate the same to a The opposite end of the winding I0 carries a terminal II so that the switch 32 may be connected with the previously mentioned circuit by means of the terminals 60 and II. A spring 12 normally urges the contact arm 51 upwardly as viewed in Fig. 4 to maintain the movable contact GI in engagement with the contact 62 carried by the spring arm 63 and these contacts are always in engagement when the winding of the electro-magnet I0 is energized except as the contacts 6| and 62 may be mechanically separated by the adjustable screw 55 carried by the lever arm 55. The purpose of the electro-magnet I0 is to exert a pull on the spring arm 63 to depress the contact end of the same while rotating the contact arm 51 so that both contacts GI and 62 are depressed whenever the electro-magnet I0 is energized. The depression of the spring arm 63 together with the contacts GI and 62 and the contact arm 51 rotates the contact 'arm in a counter-clockwise direction as viewed in Fig. 2 and away from the lever arm 55 and adjustable screw 56 so that a higher pressure must be reached within the tank 25 for the screw 56 to break the contacts GI and 62 than would be'the case if the'electro-magnet III were not energized. 7

With the electro-magnet I0. de-energized the resiliency of the spring arm 63 urges it upwardly as viewed in Fig. 4 against a stop 13 shown in Figs. 2, 3 and 8. The spring I2 urges the contact arm 51 in a clockwise direction to maintain the contacts BI and 32 in engagement unless the contact 6| is mechanically held in separated position by means of the screw 56 carried by the arm 55 anasss and operable by the lever 4|. The resiliency of the arm 63 also serves to cause a snap break oi.- the contacts 6| and 62 when the circuit through switch 32 is mechanically broken by the adiustable screw 56 carried by the lever 55. This snap action prevents severe arcing at the contacts and burning out of the latter.

When the pressure in tank reaches a certain predetermined value, the arm 4| and lever arm .55 will be rotated in a clockwise direction as viewed in Fig. 2 until the screw 56 mechanically separates the contact 6| from the contact 62 de- 4|, 1. e., rotation of the lever 4| and lever arm55 in a counter-clockwise direction, this lever and lever arm must rotate to a position corresponding to a lower pressure in the tank 25 before the contact arm 51-can allow the movable contact 6| again to engagethe contact 62 to complete the circuit through the switch and again energize the bore 8| and rotatablyv mounted on a pivot pin electro-magnet I6. Energization of the electromagnet 16 will again depress the spring arm 63 but the contacts 6| and 62 will remain in engagement since the leverarm and stop 56 are receding away from the switch arm 51.' 'In this manner the switch 32 is open at a higher pressure within the tank 25 than the pressure within the tank at which the switch will again close. This operation of the switch 32 avoids fluttering or hunting of the control of the load control valve 22 of the. compressor l3.

The switch 32 is employed to control the operation of the load control valve 22 for the compressor i3. Referring to Figs. .5 and 6 in which this valve is shown more in detail, the valve includes a body 86 provided with a cylindrical bore 8| adapted to extend between the bore of the intake conduit 2| and the intake manifold 26.

A disc valve 82 is arranged within the cylindrical 84 by fastening the disc valve within a radially extending slot 83 projecting throughthe axis of the shaft by means of screws 85. The valve ele-' ment 82 is adapted to be operated to two, positions, one position being the fully open position illustrated in Figs. 5 and 6 in which the element 82 is arranged axially of the cylindrical bore 8| and the other position of the valve element being at right angles to the illustrated position in which the valve disc 82 fully closes the cylindrical bore 8|, (vertical position of valve. disc, Fig. 8) in which the axis of the cylindrical bore 8|.

82 is adapted to be operated to the fully openpoposition it is disposed normally with respect to The valve disc sition illustrated in Figs. 5 and 6 by means of a solenoid 88 including a movable armature 81 connected by an adjustable link 86 to-a double arm lever: 5| fixed to the shaft 84. The solenoid 66 is adapted to operate the disc valve element 82 against the bias of'a spring .92 -extending between the body member 86 and the opposite arm of the lever 8| from that arm to-which the link 98 is connected. The solenoid 88 has its winding connected in series in the above mentioned circuit, (Fig. 8), and the contacts 6| and 62 are connected in series with the winding of solenoid 86 so that the valve disc 82 is in open position whenever the circuit is energized and the contacts 6| and 62 are closed. The energization of the cirthe compressor is operated continuously at speeds in proportion to the demand by air from the air tank 25. Upon starting the engine l2 it accelerates until a speed is reached for which the speed governing device 3| is set. This speed may be.

for example, 1200 R. P. M. of the compressor. Any tendency of the engine l2 to operate at higher speeds will cause the speed governing mechanism 3| to rotate the control lever 58 in a clockwise'direction against the tension of the spri 52 and through the link 54, restrict the delivery of fuel to the carbureting mechanism 38 of the engine l2 to reduce its speed to the value for which the speed governing mechanism 3| is set. With little or no delivery of air from the air tank 25, the pressure within this tank will be built up to a value of approximately pounds per square inch when the speed of rotation of the compressor has reached approximately 1200 R. P. M. Continued rotation of the compressor will build up higher pressures within the air tank and pressures above 80 pounds per square inch will, be communicated to the head surface 3'! of the bellows 34 and over come the biasing action of the spring 35 so that the bellows 34 will move to the left as viewed in Figs. 2 and 8. This movement of the bellows 34 will cause clockwise rotation of the lever 4| and through the spring 52 and arm 53 will cause a corresponding rotation of the arm 56 which will in turn cause a reduction of the amount of fuel admitted to the engine I! and a reduction in its speed. The circuit containing the switch 32 and the winding of the solenoid 86 in series with contacts 6| and 62, is energized during. the operationof the engine 2 from a storage battery 56 and controlled by a switch 81 which may be the' ignition switchfor engine l2.

Since at lower speeds of the engine and at lower pressures within g the tank 25 the stop screw 56 is spaced from the switch arm 51, the contacts 6| and 82 are closed rotation of the control lever 56 of the speed governing mechanism andconsequent reduction of the fuel delivered to the engine i2 and a reduction in its speed. With little or no demand for air from the tank 25 the s'peedoi rotation of'the compressor will have been gradually reduced to a value of approximately 510 R. P. M. When a pressure of pounds per square inch is attained within the air tank 25 the adjustable stop screw 56 will have made contact with the pivoted contact arm 51 of the switch 32 and pressures above 105 pounds within the tank 25 will depress the contact lever 51 and open the contacts 6| and 62. As these contacts are mechanically opened, the encrgization of the winding of the electro-magnet I8 is cut off and the spring arm 63 will snap to an elevated position against the stop 13 which snap action of the contact and the rapid separation of the same will reduce arcing and burning out of these contacts. Separation of the contacts 5i and 62 will cause de-energization of the winding of the solenoid 86 and throw the control of the load control valve 22 upon the spring 92 which causes a closing of the valve disc-82 shutting off further delivery of air to the air compressor.

As long as the pressure within the tank 25 remains above, for example 97 to 100 pounds per square inch, the engine and compressor will operate at idling speed with the load control valve 22 of the compressor in fully closed position. If the pressure within the air tank 25 is reduced through the delivery of air or leakage or other causes, the pressure within the pressure responsive means 30 is also reduced allowing the piston to move to the right under the influence of the spring 35 which allows counter-clockwise rotation of the lever ll and clockwise rotation of the a contact arm 51 of the switch-32.

arm 5'! follows the screw 56 until the contacts.

The contact -to bring the contacts GI and 62 into engagement with the spring arm 63 in its elevated position. In this manner the contacts are mechanically broken upon increasing pressures within the pressure tank and the pressure responsive device 30 as soon as a pressure approximately I05 pounds per square inch or over is attained, whereas the contacts areagain made only when the pressure within the tank 25 and pressure responsive means 30 has dropped to a value of approximately 97 to100 pounds per square inch. This differential of pressure between the points at which the contacts are mechanically broken and then made prevents fluttering or hunting in the control of the intake valve for the compressor,

The making of the contacts 6| and 62 upon retractive rotation of the lever 4| and lever arm 55 causes energization of the solenoid 86 and the opening of the compressor load control valve 22. If the demand 'for air from the tank '25 is not excessive the retractive movement of the lever 4| through the spring 52 and arm 53 of the lever 50 increases the amount of the fuel delivered to the carbureting means 38 for the engine l2 so that this'engine speeds up driving the compressor at a correspondingly increasing rate so as to increase the pressure within the tank 25 until a pressure of approximately 105 pounds is again reached at which point the contacts GI and 62 are again broken and the intake valve to the compressor closed. The normal operating range of pressures within the air tank 25 is between 80 and 105 pounds per square inch and between approximately ,97 to 105 pounds when the load which the contacts SI and B2 are closed the engine. In the event of excessive demands for air from the pressure tank 25, there will be a further retraction of the lever 4| and a consequent further increase in the amount of the fuel delivered to the engine which will cause a further speeding up of the engine l2 and compressor l3 and additional delivery of such air from the compressor l3 to the tank 25 to again bring the It will be noted that during the operation of the compressor load control valve 22 that the valve disc 82 is snapped to fully open or fully closed position by the action of either the solenoid 86 or-the spring 92. Consequently, there is little or no throttling action of the valve upon air drawn into the compressor. Throttling of air brought into the compressor would be undesirable since this would cause heating of the air which in addition to the heat due to compression of the air within the compressor cylinders would raise the temperature oi. the delivered air. to undeslrable values. By avoiding throttling of the air at the intake valve of the compressor-the temperature of the delivered air is reduced resulting in less carbonization of oil and insuring proper lubrication of the cylinder walls of the compressor, minimizing the danger of fire and explosion,

and at the same time giving longer life of hose and less freezing of tools.

As many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in I a limiting sense.

What I claim is:'

1. In combination, an air compressor, a load control valve for said compressor operable to open and closed positions independently of the. operating parts of said compressor to admit and compressor, means for delivering air from the.

tank, speed control means for controlling the speed of operation of said motive means, valveoperating means for overcoming the action of said first named valve operating means and to open said valve, means responsive to the pressure in said tank for controlling the operation of said speed control means, and means operable by said pressure responsive means and in response to a predetermined pressure in said tank for rendering. inoperative said second named valve operat- -'ing means whereby saidfirst named valve operating means closes said valve.

2. In combination, an air compressor, a load control valve for said compressor operable to open and closed positions to admit and to prevent admission of air to said compressor, valve operating means normally tending to close said valve, an air tankcommunicating with said compressor for receiving air delivered by the compressor, motive means for operating said compressor, means for delivering air from the tank, speed control means for controlling the speed of operation of said motive means, valve operating means for overcoming the action of said first named valve operating means and to open said valve, means responsive to the pressure in said tank for controlling the operation of said speed control means, and means operable by said pres-. sure responsive means and in response to a pre-.

determined pressure in said tank for rendering inoperative said second-named valve operating means whereby said first named valve operating means closes said valve and operable in response to another predetermined pressure in said tank materially lower than said first named predetermined pressure for rendering said second named valve operating means operative to overcome the action of said first named valve operating means and open said valve.

3. In combination, an air compressor, an ai intake valve for said compressor operable to open and closed positions, to load and unload said compressor, spring means normally acting to close. said valve and prevent admission of air to I the compressor, an air tank communicating with said compressor for receiving air discharged from the compressor, motive means for operating said compressor, means for delivering air from said tank, speed control means for governing the operating speed of said motive means,"electr omagnetic means operable in the absence of pressures above a predetermined value in said tank for overcoming said spring means and maintaining said intake'valve in open position,- means responsive to the pressure in said tank for controlling-the operation of said speed control means, and means operable by said pressure responsive means and in response to pressure above said predetermined value' in said tank for rendering in;

' operative said electro-magnetic valve operating means whereby said spring means closes said valve.

4. In combination, an air compressor, an air intake valve for said compressor operable to open and closed positions to load and unload said. compressor, spring means normally acting to close said valve and prevent admission of air-to the compressor, an airtank communicating with said compressor ior'receivlng air discharged lrom the compressor, motive means' for operating said compressor, means for delivering air from said tank, speed control .means for governing the operating speed of said motive means, electromagnetic means operable in the absence of pressures above a predetermined value in said tank for overcoming said spring means and maintaining said intake valve in open position, means responsive to-the pressure in said tank for controlling the operation of said speed control means, and means operable by said pressure responsive means and in response to pressures above said predetermined value in said tank for rendering inoperative said elec'tro-magnetic valve operating means whereby said spring means closes said valve and operable in response to an other predetermined pressure in said tank matean arm rotatable in one direction in response to increasing pressuresin'said tank and rotatable inthe opposite direction in response to decreasing pressures in said tank, valve operating means acting to shutsaid load control valve, electromagnetic means operable to overcome said firstnamed valve operating means and open said load control valve, and a switch operable upon rotation of said arm in said one direction in response to one predetermined pressure in said tank to cause de-energization of said electro-magnetic means wherebysaid valve operating means becomes effective to shut said load controlvalve and operable'up'on rotation of said arm in said opposite direction in response to another pressure in said tank materially lower than said one predetermined pressure to energization of said electro-magnetic means whereby the latter becomes efiective to open said load control valve.

6. Inc, control system for an air compressorincluding motive mean's for operating said compressor, a load control valve for said compressor operable to fully open and fully shut positions, an

' air tank for receiving air delivered by said compressor and having means for delivering air therefrom, the combination or, means for controlling the speed of operation of said motive means in response to the pressure in said tank and including an arm rotatable in one direction in response to increasing pressures in said tank and rotatable in the opposite. direction in response to decreasing pressures in said tank, valve operating means acting to shut said load control valve, electromagnetic means operable to overcome theaction of said first-named valve operating means and open said load control valve, and a switch operable uponrotation of said arm insaid. one direction in response to one predetermined pressure in said tank tocause de-energization of said electro-magnetic means whereby said valve operating means becomes effective to shut said load control valve and operable upon rotation of said arm in said opposite direction in response to, another pressure in said tank materially lower than said one predetermined pressure to cause energization of said elec'tro-magnetic'means whereby the latter becomes efiective to open said lead control valve.

1 ALLEN C. STALEY. 

